Miscellaneous Mechanical Components
DOE-HDBK-1018/2-93
STEAM TRAPS
The valve is attached to the bellows in such a way that the valve closes when the bellows
expands. The valve remains closed, trapping steam in the valve body. As the steam cools and
condenses, the bellows cools and contracts, thereby opening the valve and allowing the
condensate to drain.
Impulse Steam Trap
Impulse steam traps, illustrated in Figure 19, pass steam and condensate through a strainer before
entering the trap. A circular baffle keeps the entering steam and condensate from impinging on
the cylinder or on the disk. The impulse type of steam trap is dependent on the principle that
hot water under pressure tends to flash into steam when the pressure is reduced.
The only moving part in the steam trap is the disk. A flange near the top of the disk acts as a
Figure 19 Impulse Steam Trap
piston. As demonstrated in Figure 19, the working surface above the flange is larger than the
working surface below the flange.
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